Zone control system



Nov. 18, 1941. L, HA IS 2,263,422

' ZONE CONTROL sYsTEM" 4' Filed April 17 5639 "zone 5 4 37 lol 5 zous c ma Inc.

T0 ZONE. (1

inventor John 1!. Harris as & KM Cltbmg Patented Nov. 18, 1941 ZONE CONTROL SYSTEM John L. Harris, Minneapolis, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware u Application April 17, 1939, Serial No. 268,184

20 Claims.

This invention relates to a temperature con-' trol system for a building which is divided in zones for conditioning purposes.

In conventional systems of this type steam other temperature changing fluid is conducted from a suitable source to heat exchangers in the various zones and a thermostatically controlled zone valve or equivalent means regulates the supply of steam to the heat exchangers of each zone for maintaining desired temperature conditions in each zone. Although su h a system usually provides accurate temperat re control, undesirable conditions often arise by reason of more than one zone valve opening or closing at substantially the same time.

In the case where the source of steam is a boiler controlled by suitable pressure controls, opening of more than one zone valve at substantially the same time places a substantially instantaneous large load on the boiler whereupon the steam pressure decreases quite an extent before the boiler can recover and maintain the desired steam pressure. This decrease in steam pressure may be so great as to prevent the proper distribution of steam throughout the system with a result that the heating system does not maintain accurate temperature conditions in the various zones. Closing more than one zone valve at substantially the same time decreases substantially instantaneously the load on the boiler whereupon the boiler pressure increases to quite an extent. This increase in steam pressure may be so great as to cause P099 8 of the boiler through its safety blow-off valves which is not conducive of economical operation. It is well established that a boiler may be operated most efficiently when the load on the same is maintained relatively constant and if the load is caused to vary rapidly as it will under the above conditions, the eificiency of operation of the boiler is accordingly reduced.

In the case where the source of steam is a central power plant or district steam supply system. substantially simultaneous opening or closing of the zone valves will vary greatly the demand for steam in the same manner as outlined above. Inasmuch as the cost of steam not only depends upon the amount of steam consumed but upon the rate at which it is consumed, the above system is relatively expensive to operate under these conditions. Further, it is not desirable to cause the steam pressures in the district steam supply system to fluctuate greatly which the above system might easily do.

The primary object of this invention is to avoid the above undesirable conditions which are inherent in a conventional zone heating system. In

'-carrying out this invention means are provided for preventing opening of the zone valves when the steam pressure decreases below a desired value and for preventing closing of the zone valves when the steam pressure is above a desired value until such time as the steam pressure is restored to the desired normal operating values. This effectively prevents large fluctuations or surges in steam pressure whereupon the heating system may be operated more satisfactorily and economically.

A further object of this invention is to provide means operative when the steam pressure is restored to the desired normal value for opening or closing first that zone valve whose temperature responsive means flrst demanded opening or closing thereof. By reason of this feature proper proportioning of steam to the various zones is at all times assured.

This improvement, which maintains the steam pressure within relatively narrow limits, has an added advantage when. applied. to a system.

wherein the zone valves are controlled by an outdoor controller of the type shown and described in Patent No. 2,065,835 granted to D. G. Taylor on December 29, 1936. By maintaining the steam pressure within relatively narrow limits the amount of heat supplied to the zone in a predetermined time interval may be quite accurately gaged and may therefore be readily balanced against the amount of heat supplied to the outdoor controller. This feature also forms an object of this invention.

Other objects and advantages will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawing.

40 For a more thorough understanding of this boilerll flred by a coal stoker, oil burner, gas

valve or other similar device designated at H. A pressure controller generally designated at 13 may control the operation of the firing device to maintain the boiler pressure at desired values. The pressure controller i3 may comprise a bellows l4 connected by a pipe i5 to the boiler ill for operating a lever l8 against the action of an adjustable tension spring 11. The lever I8 in turn operates a mercury switch i8 and for purposes of illustration it is assumed that the switch I8 is moved to a closed position when the boiler pressure decreases to 4 lbs. and is moved to an open position when the boiler pressure increases to 6 lbs. Power is supplied to the firing means I l by means of line wires l3 and 28 leading from some source of power, not shown. When the pressure on the boiler decreases to 4 lbs. a circuitiscompleted from the line wire l3 through the mercury switch I8 and firing device ll back to the other line wire 28 to place the firing'means H in operation. When the boiler pressure increases to 6 lbs. the above circuit is opened and the firing means II is stopped. In this manner the steam pressure in the boiler I0 is maintained between 4 lbs. and 6 lbs.

A header 22 supplies steam from the boiler Hi to risers 23, 24, and'25 which extend to the heat exchangers in zones A, B, and C, respectively. The supply of steam to zone A is controlled by a valve 28 operated by a two position electric motor 23 and the supply of steam to zones B and C may be controlled by valves 21 and 28, respectively, which in turn are controlled by two position electric motors 38 and 3|, Thus the supply of steam. to the various zones is individually controlled by zone valves.

The motors or the zone valves 28, 21, and 28 are respectively controlled by relays generally designated at 33, 34, and 35. The relays 33, 34, and 35 are in tum-controlled by temperature responsive controllers 38, 31 and 38, respectively, the controller 38 being associated with zone A and the controllers 31 and 38 being associated respectively with zones B and C. When the temperature responsive controller 38 of zone A demands heat, the relay 33 is operated to open the zone valve 28 to supply heat to zone A and when the temperature responsive controller 38 becomes satisfied the relay 33 is operated to close the zone valve 28. In a like manner the temperature responsive controllers 31 and 38 of zones B and C operate through their relays 34 and 35 to open and close the zone valves 21 and 28 which control the supply oi'steam to the heat exchangers of zones B and C. A relay generally designated at 33 controls all of the relays 33, 34, and 35 to prevent operation or the relays when any zone valve is opening or closing.- A pressure controller generally designated at 40 also controls all of the relays 33, 34, and 35 to prevent operation of the relays and hence operation of the zone 'valves whenever the steam pressure is above or below predetermined values.

Although the temperature responsive controller 38 of zone A may be a conventional thermostat responding to the temperature within zone A, it is shown for purposes or illustration to be an outdoor controller of the type shown and described in Patent No. 2,065,835 granted to D. G. Taylor on December 29, 1936. This temperature responsive controller is located outside of the building immediately adjacent the zone which it controls so that it is responsive to the same atmospheric conditions including temperature, wind, and solarradiation that affect its associated zone. The temperature responsive controller may comprise a mass in the form 0! a metallic block 42 in which is located a thermostatic element 43. The thermostatic element 43 responds to the temperature of the block 42 and operates contacts 44 and 45 with respect to adjustable stationary contacts 48 and 41, respectively. An'electric heater 48 is intimately associated with block 42 for heating the same and this heater has suificient capacity to maintain the block 42 at a desired temperature regardless responsive controllers is not deemed necessary.

The relay 33 controlled by the temperature responsive controller 38 of zone A may comprise an operating coil 52 for operating switch arms 53, 54, and 55. When the operating coil 52 is energized, the switch arms 53, 54, and 55 are moved into engagement with contacts 58, 51, and 58, respectively, and when. the operating coil 52 is deenergized the switch arms 53, 54, and 55 are moved out of engagement with their respective contacts by means of springs, gravity or other means not shown and the switch arm 55 is moved into engagement with a stationary contact 58. The relay 33 may also include a stepdown transformer-having a secondary 8| and a primary 82 connected by wires 83 and 84 across line wires 85 and 88 leading from some source or power, not shown. The step-down transformer 88 is utilized for supplying power to the control circuits of the relay 33 as well as for supplying power to the heater 48 of the outdoor controller 38. The construction of the relays 34 and 35 is exactly the same as the relay 33 and therefore a description of these relays is not considered necessary.

The relay 33 maycomprise an operating coil 10 for operating switch arms 1|, 12, 'HB, 123, 1IC, and 120. When the operating coil 10 is energized the switch arms 1|, HE, and "C are moved into engagement with contacts 13, 13B, and 13C and the switch arms 12, 12B, and 120 are moved out oi? engagement with contacts 14, 14B, and 140. When the operating coil 18 is deenergized the switch arms 1!, HE, and HC are moved out of engagement with their respective contacts and the switch arms 12, 12B, and 120 are moved into engagement'with their respective contacts by means of springs, gravity, or other means, not shown.

The pressure controller 40 may comprise a bellows 18 connected by a pipe 18 to theheader 22 for operating a lever 88-against the action of an adjustable tension spring 8|. The lever operates a shaft 82 upon which are mounted thermostatic elements 83, 84, 83B, 84B, 83C, and 840 which in turn carry mercury switches 85, 86, B, 85B, 85C, and 880, respectively. The switches 85, 85B, and 850 are normally open as shown and the switches 88. 88B, and 88C are normally closed as shown. Upon a rise in steam pressure the mercury switches are tilted in a counter-clockwise direction by the shaft 82 as indicated by the arrow dlbignated "rise" and upon a drop in pressure these mercury switches are tilted in a clockwise direction as indicated by the arrow designated drop.

For purposes of illustration it is assumed that when the pressure drops to 2 Has, the mercury switches 86, 86B, and 860 are opened and when the pressure rises to 8 lbs. the mercury switches 85, 65B, and 85C are closed. Between these pressure values the mercury switches assume the positions shown in the drawing. The thermostatic elements 83, 83B, and 83C are provided with heaters 81, 61B, and 81C, respectively, and when the heaters are energized they tend to flex the thermostatic elements to the left as indicated by the arrow designated H. The thermostatic elements 84, 84B, and 840 are provided with heaters 68, 88B, and 88C and when these heaters are energized they operate to flex the thermostatic elements to the right in the direction indicated by the arrow designated H.

Power is supplied to the two position electric motors 29, 36, and 3| by means of line wires 90 and 9| leading from some source of power, not shown. The power terminals 92 and 93 of these two position motors are connected in parallel across the line wires 90 and 9 I. The motors 29, 30, and 3| are of the two position type which require power only when the motors are being operated from a closed position to an open position or from an open position to a closed position. When the motors are stationary, that is, either open or closed, they do not require power. The operating coil 10 of the relay 39 is connected in series with the power supply leading to the zone valve motors 29, 36, and 3| so that the operating coil I6 is energized when any of the zone valve motors are operating. The zone valve motors are provided with control terminals 94, 95, and 96 for controlling the operation thereof. When a circuit is completed across the control terminals 94 and 95 the zone valves are moved to closed position and when a circuit is completed across the control terminals 95 and 96 the zone valves are moved to open position.

With the parts in the position shown in the drawing a decrease in temperature in the outdoor controller 36 of zone A to 65 causes the contacts 44, 46 and 45, 41 to close to complete a starting circuit for the operating coil 52 of the relay 33. This starting circuit may be traced from the secondary 6| of the step-down transformer 60 through wires I08 and llll, contacts 46, 44, 45, and 41, wire I92, contact 14 and switch arm 12 of relay 39. wire I03, mercury switch 86 of the pressure controller 48, wires I64 and I65, operating coil 52 and wire I66 back to the secondary 6|. Completion of this starting circuit energizes the operating coil 52 to move the switch arms 53,54, and 55 into engagement with contacts 56, 51, and 56.

Movement of the switch arm 54 into engagement with the contact 51 completes a circuit from the secondary 6| through wire I06, contact 51, switch arm 54, wire |||9, variable resistance 6, wire I, heater 48 of the outdoor controller 36 and wire ||2 back to the secondary 6|. Completion of this circuit energizes the heater 48 to heat the outdoor controller 36 and the amount of heat supplied by the heater 48 to the outdoor controller 36 is determined by the variable resistance H6. i

Movement of the switch arm 55 into engagement with the contact 56 completes a circuit from the control terminal 95 of the zone valve motor 29 through wire H5, switch arm- 55, contact 58 and wire H4 to the control terminal 96. Completion of this circuit causes opening of the zone valve 25 for zone A. Heat is therefore beswitch arm 53, wire I65, operating coil 52 and wire I66 back to the secondary 6|. Completion of this main maintaining circuit maintains the operating coil 52 energized until such time as the temperature within the outdoor controller 36 increases to 70 to separate the contacts 44 and 46. When this occurs the operating coil 52 is deenergized to move the switch arms 53, 54, and out of engagement with their associated contacts and to move the switch arm 55 into engagement with the contact 59. Movement of the switch arm 54 out of engagement with the contact 51 deenergizes the heater 48 o! the outdoor controller 36. Movement of the switch arm 55 into engagement with the contact 59 completes a circuit from the control terminal 95 of the zone valve motor 29 through wire 5, switch arm 55, contact 59, and wire 9 to the control terminal 94. Completion of this circuit operates the valve motor 29 to close the zone valve 26 whereupon the supply of heat to zone A is interrupted. The operating coil 52 of the relay 33 cannot again be energized until such time as the temperature of the outdoor controller 36 decreases to 65 and when this occurs the above outlined sequence of operation againtakes place. The outdoor controller 36 of zone A therefore operates the relay 93 to open the zone valve 26 for zone A and to energize the heater 48 of the outdoor controller 36 upon a demand for heat and when the demand for heat is satisfied the relay 33 is dropped out to close the zone valve 26 and to deenergize the heater 48. By properly adjusting the variable resistance I I0 the heat inputs to the outdoor controller 36 and to zone A may be proportioned in accordance with the heat losses from the outdoor controller and the zone whereby substantially constant temperatures are maintainedwithin zone A as well as within the outdoor controller 36.

The construction and sequence of operation outlined immediately above in connection with zone A are the same for zones B and C and accordingly like reference characters have been utilized for like parts and wiring connections, the reference characters for zone'B being designated 13 and the reference characters for zone C being designated C. It is therefore seen that the outdoor controllers 36, 31, and 38 control the operapasses in series through the switch formed by the switch arm 12 and the contact I4 of the relay 39. Hence when either zone valve 21 or 28 is operating it is impossible to pull in the relay 33 to open'the zone valve 26. In a like manner the starting circuits for relays 34 and 35 pass through the switches formed by the contacts 14B and 14C and the switch arms 12B and 12C of the relay 30 so that these relays cannot be pulled in when any zone valve is operating. Accordingly after one zone valve has started to open it is impossible for any of the other zone valves to open until after that zone valve has been completely opened. a

If now one of the zone valves should open and as a result the steam pressure drops to 2 lbs. to open the mercury switches 88, 88B, and 880, it is impossible to open any of the other zone valves since the strating circuits for the operating coils 52 of the relays 33, 84, and 38 also extend through these mercury switches. Accordingly when the steam pressure decreases below, illustratively, 2 lbs it is impossible to open any of the zone valves until such time as the steam pressure is restored to substantially the 2 lb. pressure value to close the switches 88, 88B, and 88C. Thus, when the steam pressure is low, opening of additional zone valves with a consequent further reduction in steam pressure is prevented. This arrangement therefore tends to maintain th steam pressure within desired limits.

The heater elements 88, 88B, and 880, which upon energization flex the thermostatic elements 84, 84B, and 84C to the right, are connected in parallel with the electrodes of the mercury switches 88, 88B, and 88C. respectively. These heating elements have sufficient resistance that they will not allow the operating coil 82 of the 32, 34, and 88 to be sufllciently energized the other switches demand pulling in of the relays. Assume now that the controller 81 of zone B hascalled for heating and has opened its zone valve. 21 with a result that th steam pressure has dropped below the 2 lb. value to open the switches 88, 88B, and 880. Also assume that s thermostatic controller of zone C is satisfied with its zone valve 28 closed but that while the steam pressure is below 2 lbs. the controller 88 ofzone A demands heat. The zone valve 28 of zone A cannot be opened at this time inasmuch as the mercury switch 88 is open. However current will flow through the heater element 88 and tend to move the mercury switch 88 toward a closed position. When the steam pressure starts to rise, the switch 88 will thererelays to pull in the relays if ating, the operating coil 10 of the relay38 is energized whereupon the relay 39 is pulled in to mov the switch arm 1I into engagement with the contact 13. This first auxiliary maintaining circuit may be traced from. the secondary 8| through wires I00, I2I, contact 13, switch arm II, wire I22, contact 88, switch arm 83, wire I08,

operating coil 52 and wire I08 back to the secondary 8|. Completion of this first auxiliary maintaining circuit maintains the relay 83 pulled in to prevent closing of the zone valve 28 while the zone valve 21 is closing. The other zone valves are prevented from closing under these conditions in a like manner. The relay 28 therefore prevents any zone valve fromv closing I while any other zone valve is in operation.

If new oneof the zone valves should close with the result that the steam pressure should rise to 8 lbs. the mercury switches 85, 85B, and 88C of the pressure controller 40 are closed and closure of these switches completes a second auxiliary maintaining circuit for the relays 88, 34, and 38. Referring to zone A this second auxiliary circuit may be traced from the secondary 8I through wires I00, I2I, and I24, mercury switch.

pressure rises above 8 lbs. it is impossible to close any zone .valve when its temperature responsive controller becomes satisfied until such time as the steam pressure decreases to substantially 8 fore close before the mercury switch 880 closes and therefore, even though controller 88 of zone C then begins to call for heat, the zone valve 28 of zone A will open before the zone valve 28 of zone C will open. In other words when one zone valve has opened with a resultant decrease in steam pressure below the 2 lb. value, the next zone valve which would be opened will be determined by the time at which its controller demands heat. Illustratively, if the controller 28 of zone A should demand heat before the controller 28 of zone C demands heat the zone valve' 28 of zone A. will open before the zone valve 28 of zone C opens. By reason of this arrangement the proper proportioning of steam to the various zones of the building will be assured and no zone will ever be starved of steam. by any other zone. Assume now that the zone valves 28 and 21 of zones A and B are opened,that the controller 81 of zone B becomes satisfied whereupon the zone valve 21 starts closing and thatthe controller 88 of zone A becomes satisfied while'the zone valve 21 of-zone B is closing. Ordinarily the zone valve 28 of zone A would close but it is mainabove when the zone valve 21 of zone B is operlbs.

1 It is here noted that while the heater 81 is in series with the mercury switch 88 it is in eifect in parallel with the contacts 44 and 48 of the controller 88 so that when the contacts 44 and 48 are closed the, heater 81 is not energized. However when the relay. 88 is pulled in and the contacts '44 and 48 separate the heater 81 becomes energized. In other words, when any controller becomes satisfied while the steam pressure is above 8 lbs. the heater 81 of that zone becomes energized to urge the mercury switch 88 associated therewith toward an open position. Thus, as the pressure decreases towards 8 lbs., the mercury switch to close that depends upon which heater was energized first and since the energization of the heater begins when the temperature responsive controllers become satisfied, then the mercury switches are closed in an order corresponding to the times at which the temperature responsive controllers become satisfied. Accordingly, if the steam pressure be above 8 lbs. and the controller 88 of zone A becomes satisfled before the controller 81 of zone B, then the zone valve 28 of zoneA will close before the zone valve 21 of zone B. This effectively prevents overheating of any zone by insuring that the zone temperature controller which becomes satisfled closes its zone valve first. v

The operation of the complete system may be summarized briefly as follows: the zone valves controlling the supply of steam or other temperature changing fluid are individually opened and closed by their temperature responsive controllers to maintain desired temperature conditions in each zone. While any zone valve is operating either to an'open position or to a closed position it is impossible to operate the other zone valves whereby substantially simultaneous opening or closing of more than one zone valve is prevented. This tends to maintain the steam pressures within desired limits. If the steam pressure should decrease below a desired value by reason of a zone valve opening it is impossible to open any other zone valve until such time as the steam pressure is restored to substantially that desired value. If the steam pressure should rise above a desired value by reason of a zone valve closing it is impossible to close any of the other zone valves until such time as the steam pressure is restored to substantially that desired value. By reason of this arrangement the steam pressure is maintained within desired limits at all times whereby large fluctuations or surges in steam pressure are effectively prevented. Satisfactory and economical operation of the heating system is therefore assured. In order to prevent underheating in any zone provision is made for opening the zone valves in an order corresponding to the time at which the 'zonetemperature controllers call for heat and likewise to prevent overheating in any zone the zone valves are closed in an order depending upon the time at which the zone temperature responsive controllers become satisfied.

While for purposes of illustration one form of this invention has been disclosed, other forms thereof may become apparent to those skilled in the art upon reference to this disclosure and therefore this invention is to be limited only by the scope of the appended claims and prior art.

I claim as my invention:

1. In a temperature control system for a building having a plurality of zones to be conditioned,

thecombination of, a source of temperature changing fluid, means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, regulating means for each zone for increasing and decreasing the supply of temperature changing fluid to its associated zone, temperature responsive means associated with each zone for controlling the regulating means of that zone to maintain desired temperature conditions in the various zones, and means associated with the regulating means and responsive to a condition of the temperature changing fluid affected by the demand for said fluid, said means being operative upon said condition varying undesirably in one direction by reason of operation oi. one of said regulating means in one manner to prevent immediate operation of another of said regulating means in the same manner, without affecting the operation of the regulating means which has already operated in that manner.

- 2. In a temperature control system for a building having a plurality of zones to be conditioned the combination of, a source or temperature changing fluid, means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, regulating means for each zone for increasing and decreasing the supply of temperature changing fluid to its associated zone, temperature responsive means associated with each zone for controlling the regulating means or that zone to maintain desired temperature conditions in the. various zones, and means associated with the regulating means and responsive to the temperature changing ability of the temperature changing fluid,

fluid decreases below a desired value to prevent operation of any oi. said regulating means to increase the supply of fluid to its zone, without affecting the operation of any regulating means which has already caused such an increase.

3. In a temperature control system for a building having a plurality of zones to be conditioned, the combination of, a source of temperature changing fluid, means for supplying temperature changing fluid from said 'source to the zones of the building for conditioning the same, regulating means for each zone .ior increasing and decreasing the supply of temperature changing fluid to its associated zone, temperature responsive means associated with each zone for controlling the regulating means of that zone to maintain desired temperature conditions in the various zones, and means associated with the regulating means and responsive to the temperature changing capacity of the temperature changing fluid, said means being operative when the temperature changing capacity of the temperature changing fluid increases above a desired value to prevent operation of any of said regu-.

lating means to decrease the supply of fluid to its zone, without affecting the operation of any has already caused such desired temperature conditions within the various.

zones, and means associated with the valve means and responsive to the pressure of the steam at said source for preventing opening of the valve means when the pressure of the steam decreases below a desired value without causing closure of said valve means it already open.

5. In a temperature control system for a building having a plurality oi. zones to be heated, the

'combinationoi, a source of steam, heat exchanger means in each zone, means for supplying steam from said source to the heat exchanger means of the various zones for heating the same, valve means for each zone for regulating the supply of steam to the heat exchanger means of. that zone, temperature responsive means associated with each zone for opening and closing the valve means of that zone to maintain desired temperature conditions within the various zones, and means associated with the valve means and responsive to the pressure of the steam at said source for preventing closing of the valve means when the pressure 01' the steam increases above a desired value without said means being operative when the temperature changing ability of the temperature changing causing opening closed.

6. In a temperature control system for a building having a plurality of zones to be conditioned,

the combination 0!, a source of temperature changing fluid. means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, regulating means for each zone for increasing and decreasing the supply of temperature changing fluid to its associated zone, temperature responsive means associated with each zone for conof said valve means i! already dition of the temperature changing fluid varies from desired values, and means operative when the condition of the temperature changing fluid is restored to the desired values for operating flrst that regulating means whose temperature responsive means first demanded operation.

7. In a'temperature control system fora building having a plurality of zones to be conditioned, the combination of, a source of' temperature changing fluid, means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, regulating means for each zone for increasing and decreasing the supply of temperature changing fluid to its associated zone, temperature responsive means associated with each zone for controlling the regulating means of that zone to maintain desired temperature conditions in the various zones, means associated with the regulat- 'ing means and responsive to the temperature changing capacity of the temperature changing fluid for preventing the regulating means from increasing the supply of temperature changing fluid when the temperature changing capacity oi the temperature changing fluid decreases below a desired value, and means operative when the temperature changing capacity of the temperature changing fluid is restored to the desired value for operating flrst that regulating means whose temperature responsive means flrst demanded increasing of the supply of temperature changing fluid.

8. In a temperature control system for a building having a plurality of zones to be conditioned, the combination of, a source of temperature changing fluid, means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, regulating means for. each zone for increasing and decreasing the supply of temperature changing fluid to its associated zone, temperature responsive means associated with each zone for controlling the regulating means of that zone to maintain desired temperature conditions in the various zones, means associated with the regulat- I ing means and responsive to the temperature changing capacity of the temperature changing fluid for preventing the regulating means from decreasing the supply of temperature changing fluid when the temperature changing capacity 01 the temperature changing fluid. increases above a desired value, and means operative when the temperature changing capacityoi the temperature changing fluid is restored to the desired value for operating whose temperature responsive means first demended decreasing oi the supply of temperature changing fluid.

9. In atemperature control system for a building having a plurality of zones to be heated, the

.a source of steam, heat exeach zone, means for supplying steam from said source to the heat exchanger means of the various zones for heating the same, valve means for each zone for regulating the supply of steam to the heat exchanger means of that zone, temperature responsive means associated with each zone for opening and closing the valve means of that zone to maintain combination of, changer means in flrst that regulating meansthe combination of, a

- switches located in the control connections ing having a plurality of zones to ious zones, means associated with the valve means and responsive to the pressure of the steam at said source for preventing opening of the valve means when the pressure of the steam decreases below a desired value, and means operative when the steam pressure is restored to the desired value for opening flrst that valve means whose temperature responsive means flrst demanded opening thereof.

10. In a temperature control system for a buildbe heated, the combination of, a source of steam, heat exchanger means in each zone, means for supplying steam from said source to the heat exchanger means of the various zones means for each zone for regulating the supply of steam to the heat exchanger means of that zone, temperature responsive means associated with each zone for opening and closing the valve means of that zone to maintain desired temperature conditions within the various zones, means associated with the valve means and responsive to the pressure of the steam at said source for preventing closing of the valve means when the pressure of the steam increases above a desired value, and means operative when the steam pressure is restored to the desired value of closing first that valve means whose temperature responsive means first demanded closing thereof.

11. In a temperature control system for a building having a plurality of zones to be conditioned, source of temperature changing fluid, means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, a valve for each zone for controlling the supply of temperature changing fluid to its associated zone, a two position electric motor for each valve Ior opening and closing the same and requiring electrical energy only when it is operating, power connections for supplying electrical energy to all of the electric motors, temperature responsive switching means associated with each zone, control connections between the temperature responsive' switching means and the electric motor of each zone for opening and closing the valves of the various zones to maintain desired temperature conditions therein, and a relay including an operating winding located in the power connections in series with all of said motors and for preventing operation of any electric motor and its associated valve when any other electric motor and its associated valve are operating.

12. In a control system, the combination of, a plurality of electric motors, power connections for supplying electrical energy to all of said motors, a control device associated with each electric motor, control connections between the electric motors and the control devices whereby the electric motors are individually controlled by their associated control devices. and a relay including an operating winding located in the power connections in series with all or said notors and switches located in the control connections for preventing operation of any electric motor when any other electric motor is operating.

- 13. In a temperature control system for a build-,

for heating the same, valve 3 2,268,422 of temperature changing fluid to its associated zone, temperature responsive means associated with each zone for operating the valve means of that zone to maintain desired temperature conditions in the various zones, means associated with the valve means for preventing operation oi any valve means while any other valve means is operating whereby the condition of the temperature changing fluid tends to remain at desired values, and means associated with the valve means and responsive to a condition of the temperature changing fluid affected by the demand for said fluid, said means being operative when the condition of the temperature changing fluid varies from the desired values to prevent operation of said valve means in a direction to cause said condition to vary further in the same direction, without changing the position of any valve means which has already operated in that direction.

14. In a temperature control system for a building having a plurality of zones to be conditioned, the combination of, a source temperature changing fluid, means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, a valve for each zone for controlling the supply of temperature changing fluid to its associated zone,

a two position electric motor for each valve for opening and closing the same and requiring electrical energy only when it is operating, power connections for supplying electrical energy to all of the electric motors, temperature responsive switching means associated with each zone, control connections between the temperature responsive switching means and the electric motor of each zone for opening and closing the valves of the various zones to maintain desired temperature conditions therein, a relay including an operating winding located in the power connections in series with all of said motors and switches located in the control connections for preventing operation of any electric motor and its associated valve when any other electric motor and its associated v-alve are operating whereby the condition of the temperature changing fluid tends to remain at desired values, control means responsive to a condition of the temperature changing fluid affected by the demand for said fluid, and switches operated by the control means and located in said control connections, said switches being operative when the condition of the temperature changing fluid varies i'rom the desired values to prevent operation or said valve means in a direction to cause said condition to vary further in the same direction, without changing the position or any valve means which has already operated in that direction.

15. In a system of the class described, the combination of a plurality or electric motor driven valves for controlling th flow of fluid from a common source to a plurality of points of distribution, power connections for supplying electrical energyto all 01 said motors, a control device associated with each electric motor, control connections between the electric motors and the 'control devices whereby the electric motors are individually controlled by their associated control devices, and a relay including an operating winding located in the power connections in series with all of said motors and switches located in the control connections for preventing operation of any electric motor when any other electric motor is operating.

16. In a temperature control system (or a building having a plurality of zones to be conditioned, the combination of, a source of temperature changing fluid, means for supplying temperature changing fluid from said source to the zonev .2 of

the building for conditioning the same, regulating means for each zone for increasing and devent operation of any of said regulating means to increase the supply of fluid to its zone and when the temperature changing capacity increases above a desired value to prevent operation of any of said regulating means to decrease the supply of fluid to its zone, said last named means being ineflective to cause operation of any regulating means which has already operated to change the supply 0! fluid to its zone.

17. In a temperature control system for a building having a plurality of zones to be conditioned, the combination 01', a source 0!- temperature changing fluid, means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, regulating means for each zone for increasing and der the regulating means to decrease the supply of creasing the supply of temperature changing fluid to its associated zone, an outdoor controller for each zone including thermostatic means and temperature changing means, means associated with each zone and controlled by the thermostatic means of that zone for controlling the regulating means of that zone and the temperature changing means of the outdoor controller of that zone to increase the supply of temperature changing fluid and energize the temperature changing means and to decrease the supply of temperature changing fluid and deenergize the temperature changing means for the purpose of maintaining desired temperature conditions in the various zones and outdoor controllers, and means associated with all of said last mentioned means and responsive to the temperature changing capacity of the temperature changing fluid for preventing the associated regulating means for a given zone from either increasing the supply of temperature changing fluid or for causing energization oi the temperature changing means 01 the controller for said given zone when the temperature changing capacity of the temperature changing fluid decreases below a desired value without causing fluid ii in fluid increasing condition or causing deenergization of ,the temperature changing means.

18. In a temperature control system for a building having a plurality of zones to be conditioned, the combination or, a source of temperature changing fluid, means for supplying temperature changing fluid from said source to the zones oi the building for conditioning the same, regulating means for each zone for increasing and decreasing the supply of temperature changing fluid to its associated zone, an outdoor controller for each zone including thermostatic means and temperature changing means, means associated with each zone and controlled by the thermostatic means or that zone for controlling the regulating means of that zone and the temperature changing means 0! the outdoor controller of that zone to increase the supply oi temperature changing fluid and energize the temperature changing means and to decrease the supply of temperature changing fluid and deenergize the temperature changing means for the purpose of maintaining desired temperature conditions in the various zones and outdoor controllers, and means asso value without causing the regulating means to increase the supply of fluid if in'fluid decreasing condition or causing energization of the temperature changing means if deenergized,

19. In a temperature control system for a building having a plurality of zones to be conditioned, the combination of, a source of temperature changing fluid, means for supplying temperature changing fluid from said source to the zones of the building for conditioning the same, regulating means for each zone for increasing and decreasing the supply of temperature changing fluid to its associated zone, an outdoor controller for each zone including thermostatic means and temperature changing means, controlling means associated with each zone and controlled by the thermostatic means of that zone for controlling the regulating means of that zone and the temperature changing means of the outdoor controller of that zone to increase the supply of temperature changing fluid and energize the temperature changing means and to decrease the supply of temperature changing fluid and deenergize the temperature changing means for the purpose of maintaining desired temperature conditions in the various zones and outdoor controllers, means associated with said last mentioned means and responsive to the temperature changing capacity of the temperature changing fluid for preventing th regulating means from increasing the supply of temperature changing fluid and preventing energization of the temperature changing means when the temperature changing capacity of the temperature changing fluid decreases below a desired value and for preventing 'the regulating means from decreasing the supply of temperature changing 10 fluid and preventing deenergization of the temperature changing means when the temperature changing capacity of the temperature changing fluid increases above the desired value, and further means associated with said controlling means 15 for preventing said associated means from changing the operation of said regulating means or from changing the condition of energization of said temperature changing m'eans until the tem- 1 perature changing fluid is of a value within said 20 desired values.

20. In a temperature controlsystem for a building having a plurality of zones to be heated, the combination of, a source of steam, heat exchanger means in each zone, means for supplying steam 5 from said source to the heat exchanger means of the various zones for heating the same, valve means for each zone for regulating the supply of steam to the heat exchanger means of that zone, temperature responsive means associated 30 with each zone for opening and closing the valve means of that zone to maintain desired temperature conditions within the various zones, means associated with the valve mean and responsive to the pressure of the steam of said' source for 5 preventing opening of the valve means when the pressure of the steam decreases below a desired value and for preventing closing of the valve means when the pressure of the steam increases above the desired value, and further means asso- 0 ciated with the valve means for preventing said last named means from changing the existing position of the valve means until the pressure of the steam is within said two desired values.

JOHN L. HARRIS. 

